Nonvolatile semiconductor memory and manufacturing method thereof

Abstract

A method for manufacturing a nonvolatile semiconductor memory device including: forming a first and a second stacked gate structures, each of which including a first polysilicon layer formed on a silicon substrate via a gate insulator, an inter-gate insulator formed on the first polysilicon layer, a second polysilicon layer formed on the inter-gate insulator, and a cap layer formed on the second polysilicon layer, respectively; forming a interlayer insulator between the first and the second stacked gate structures, the interlayer insulator covering upper surfaces of the cap layer; planarizing the interlayer insulator by using the cap layers as a stopper; removing the cap layers so that the second polysilicon layers are exposed; masking the exposed second polysilicon layer of the first stacked gate structure by a photoresist film; removing the second polysilicon layer and the inter-gate insulator of the second stacked gate structure so that the first polysilicon layer of the second stacked gate structure is exposed; removing the photoresist film so that the second polysilicon of the first stacked gate structure is exposed; and forming conductive material layers, including a metal, on the exposed first polysilicon layer of the second stacked gate structure and the exposed second polysilicon layer of the first stacked gate structure.